A plasma display device employing a plasma display panel has such an advantage that the same allows thinning and conversion to a large screen. This plasma display device utilizes light emission in discharge of a discharge cell forming a pixel thereby displaying an image. The plasma display panel emits light in a binary manner, and hence a sub-field method displaying half tone by temporally superposing a plurality of binary images weighted respectively is employed.
In this sub-field method, one field is temporally divided into a plurality of sub-fields, and the respective sub-fields are weighted respectively. The weight of each sub-field corresponds to the quantity of light emission of each sub-field, the emission frequency is employed as the weight, for example, and the total of the weights of the respective sub-fields corresponds to the luminance of a video signal, i.e., the gray level.
When employing the aforementioned sub-field method, the eyes of a viewer follow a dynamic image with respect to the dynamic image, and hence a temporal integral area of the eyes spatially changes and specific pseudo-contour noise is observed with respect to the dynamic image. This contour line is referred to as pseudo-contour noise (“Pseudo-Contour Noise Observed in Pulse Duration Modulation Dynamic Image Display”: Technical Report of Television Institute, Vol. 19, No. 2, IDY95-21, pp. 61-66), serving as a cause deteriorating the picture quality.
In order to reduce the aforementioned dynamic image pseudo-contour, there is the one dividing one field into 10 sub-fields and setting the weights of the respective sub-fields to 1, 2, 3, 4, 5, 6, 8, 10, 11 and 13, for example. In this case, the dynamic image pseudo-contour can be reduced.
There is also the one multiplying the number of light emission pulses of each sub-field by an integer with respect to a reference number of light emission pulses, dividing one field into 10 sub-fields, for example, and setting weights for the respective sub-fields to 4, 8, 12, 16, 20, 24, 32, 40, 44 and 52 in order to improve the maximum luminance. In this case, the maximum gray level reaches 252, and the maximum luminance can be improved.
In the former example, however, the maximum gray level reaches 64 and the maximum luminance cannot be improved although the dynamic image pseudo-contour can be reduced. In the latter example, the maximum gray level reaches 252 and the maximum luminance can be improved, while the gray level can only be set every four and hence reproducibility for low gray levels lowers.